The scanning probe microscopes (SPM) have a measuring resolution of atomic order and are used in various fields such as surface configuration measurements. A scanning probe microscope maintains a distance of the order of nanometer between its probe and a sample so that fine configurations be measured by detection of a physical quantity such as tunneling current or atomic force that occurs between the probe and the sample. Among others, an atomic force microscope (AFM) is suitable for high-resolution detection of the sample surface configuration and is used in measurements of surface configuration of semiconductors, optical disks, biological samples, etc.
The requirements for such scanning probe microscopes have recently been increased, however, for high-resolution measurements and for measuring those portions such as the interior of a trench that has not been reached by a probe heretofore. It is becoming difficult to meet such requirements by those scanning probe microscopes using a conventional Si-made cantilever that is available on market.
In recent years, on the other hand, researches are widely conducted on carbon nanotube (hereinafter referred to as CNT) which is currently formed for the most part using thermal decomposition and arc discharge. According to such methods of forming CNT, a tube having high aspect ratio can be formed as having a length of several μm to as long as several-ten μm in the axial direction as opposed to its diameter of several nanometer to several-ten nanometer. It is also known that such a carbon nanotube is almost completely graphitized and has bonding state equal to or exceeding that of a diamond which has a high level of hardness. It is exceptionally excellent in mechanical strength characteristics.
For this reason, attention is drawn to the use of CNT as a probe of SPM cantilever. For example, Japanese Patent No. 3441397 has proposed a method where CNT is previously grown/formed in a separate apparatus and a manipulator is used to adhere the CNT to a probe terminal end portion of SPM cantilever.
Shown in FIG. 1 is the construction of such previously proposed SPM cantilever having CNT. FIG. 1 includes: a probe 101; a cantilever portion 102; and CNT 103 attached to a probe terminal end portion 101a. Numeral 103a indicates an effective length of CNT 103 and 103b indicates a portion of CNT 103 along which it is adhered to the probe terminal end portion. The SPM cantilever having such construction where CNT 103 is formed as adhered to the probe terminal end portion 101a has a radius of curvature as small as nanometer order at its terminal end. The resolution obtained therefrom is high. It is also excellent in wear resistance and has an advantage that, even if the terminal end of CNT 103 is worn, the radius of curvature of the terminal end coming forth of CNT 103 is unchanged as is the lead of a pencil. Thereby a high resolution can be maintained even after it is used to scan a large number of sample surfaces.
Also, since CNT features an excellent flexibility, the tube itself is flexible so that data can be obtained without damaging a sample even when the sample is soft as a biological sample. Naturally, the feature that CNT is used in forming a probe having high aspect ratio can be applied so as to enable the probe to reach deeper into a trench whereby the configuration of the trench can be faithfully measured even when a deep trench configuration is scanned.
When a manipulator is used to attach CNT 103 to the probe terminal end portion 101a of the cantilever, the bonding strength thereof is weak and an excessive vibration or pressure might cause the adhering portion 103b to come off from the probe terminal end portion 101a. Further, a reduction in the aspect ratio of the probe occurs if a large amount of an adhesive or the like is applied to the bonding portion between the adhering portion 103b of CNT and the terminal end portion 101a of the probe 101 in order to increase the bonding strength thereof. Furthermore it is difficult to control the angle and/or direction at which CNT 103 is attached to the probe terminal end portion 101a and the forming of a probe with a reproducible CNT is also difficult because of the one-by-one work to be done. Moreover, a resistance occurs between CNT 103 and the probe 101 due to the fact that the two are bonded to each other by adhesion, where very small electrical characteristics cannot be measured.
In another method, CNT is formed through a catalyst metal by means of CVD method. In this case, although growth/formation of a large quantity of CNT is possible, the selective forming of a piece of CNT from the probe terminal end portion with controlling the direction of its growth is very difficult. Also, since the catalyst metal is formed all over the lever portion and/or support portion, a large number of CNT are caused to grow not only at the probe terminal end portion of SPM cantilever but also from the sides of the probe and/or the lever portion and/or the support portion. Especially the CNT occurring from the sides of the probe has an adverse effect for example on AFM measurements.
In view of the above problems, it is an object of the present invention to provide SPM cantilever having a probe capable of stable, high resolution measurements with providing high reliability and excellent durability. It is another object of the invention to provide a manufacturing method of SPM cantilever capable of highly reproducible manufacture with using simple methods. It is a further object of the invention to provide SPM cantilever and manufacturing methods thereof having an optimal probe structure or characteristic according to its use and also to provide optimal materials for use in such manufacturing method.